1. Field of the Invention
The invention relates to colored oxidized aluminum effect pigments, a method for their production and the use thereof. The invention furthermore relates to a coating agent and a coated object.
2. Description of Related Art
Aluminum effect pigments offer a large number of possible uses and are established in diverse fields of use. They are often to be encountered, for example, in cosmetics, in the automobile sector, in the production of plastics, in paints or the printing industry. In addition to optical properties, they also offer, for example, specific technical properties here. Due to their platelet-shaped form, aluminum effect pigments display interesting optical effects, which is to be attributed to their larger reflective surface. In addition to the basic shape of the effect pigments per se, various surface modifications have furthermore been developed in the past in order to create new properties or to influence the existing properties in a targeted manner.
For example, U.S. Pat. No. 5,964,936 A describes a controlled wet-chemical oxidation of the surface of aluminum effect pigments, which are marketed by Eckert under the name Aloxal. A characteristic surface structure forms here, which brings about a coloring of the effect pigments as a consequence of interference effects. Although the champagne color shades, for example, which can be achieved by this means offer a highly interesting color spectrum for many uses, the water contained in the aluminum oxide layer can bring about a subsequent oxidation, with the result that a long-term color stability can be achieved only with difficulty.
U.S. Pat. No. 5,931,996 A describes a method for the production of colored aluminum effect pigments, wherein color pigments are introduced into a metal oxide coating of the aluminum effect pigments.
US 2007/0104663 A1 furthermore describes the coating of wet-chemically oxidized aluminum particles with a metal chalcogenide layer. Particles obtained here have a minimal total thickness and firmly adhering oxide layers, and are acceptable in terms of safety.
US 2008/0249209 A1 moreover describes the production of inorganic/organic mixed layers having an inorganic network and at least one organic component. It has been found that the production of such inorganic/organic mixed layers is elaborate in terms of process technology.
Known from US 2009/0264575 A1 are metal effect pigments having a coating which contains oligomeric and/or polymeric binders which are chemically crosslinkable and/or can be crosslinked under the action of heat, IR radiation, UV radiation and/or electron beams.
U.S. Pat. No. 6,761,762 B1 discloses effect pigments coated with reactive orientation aids. The subject of this patent is constituted substantially by aluminum effect pigments which can be coated with a coating of metal oxides or polymers. Orientation aids which make possible a covalent binding to the binder of a paint or a varnish are then arranged on this coating.
Finally, metal effect pigments, in particular aluminum effect pigments, coated with synthetic resin are known from U.S. Pat. No. 5,332,767 A.
US 2009/0117281 A1 describes aluminum effect pigments comprising an adhesion promotion layer and a polymer layer. The aim here is to be an improved water resistance and chemical resistance of the pigments.
US 2010/0152355 A1 furthermore describes metal effect pigments which are provided with a synthetic resin coating, wherein the synthetic resin coating comprises a polymer and an organofunctional silane.